The reaction of tantalum dioxide molecule with dinitrogen has been studied by matrix isolation infrared spectroscopy. The tantalum dioxide molecules produced from laser evaporation of bulk Ta2O5 target reacted with dinitrogen to form the TaO2(eta(1)-NN)(x) (x = 1-3) complexes on annealing, in which the N-2 ligands are end-on bonded to the tantalum metal center. The TaO2(eta(1)-NN)(3) complex decomposed to TaO2(eta(1)-NN)(2) under infrared irradiation. The TaO2(eta(1)-NN)(2) and TaO2(eta(1)-NN)(3) complexes rearranged to the less stable TaO2(eta(1)-NN)(eta(2)-N-2) and TaO2((eta(1)-NN)(2)(eta(2)-N-2) isomers under visible light excitation. Both the mono- and bis-dinitrogen complexes were predicted to have (2)A' or (2)A(1), ground states arising from the (2)A(1), ground state of TaO2, whereas the two tridinitrogen complexes were predicted to have B-2(2) ground states with C-2v symmetry, which are derived from the B-2(1) excited state of TaO2.